Stabilizing a hydrocracked lube oil by solvent extraction

ABSTRACT

Process of preparing lubricating oils of improved quality stability in color and sludge formation of oils hydrogenated at temperatures above 650* F. by serially extracting same subsequent to hydrogenation with a solvent having preferential solubility for aromatics.

United States Patent [1 1 Thompson STABILIZING A HYDROCRACKED LUBE OIL BY SOLVENT EXTRACTION [75] Inventor: Sheldon L. Thompson, Glen Mills,

[73] Assignee: Sun Oil Company of Pennsylvania,

Philadelphia, Pa.

[22] Filed: Sept. 1, 1972 [21] Appl. No.: 285,709

Related US. Application Data [63] Continuation-impart of Ser. No. 875,502, Nov. 10, 1969, abandoned, which is a continuation-in-part of Ser. No. 530,580, Feb. 28, 1966, abandoned.

[52] US. Cl. 208/96, 208/18 [51] Int. Cl C10g 13/02 [58] Field of Search 208/18, 19, 96

[56] References Cited UNITED STATES PATENTS 3,414,506 12/1968 Campagne ..208/309 451 Dec. 25, 1973 Primary Examiner-Herbert Levine Attorney-George L. Church et a1.

[5 7] ABSTRACT Process of preparing lubricating oils of improved quality stability in color and sludge formation of oils hydrogenated at temperatures above 650 F. by serially extracting same subsequent to hydrogenation with a solvent having preferential solubility for aromatics.

19 Claims, No Drawings STABILIZING A I-IYDROCRACKED LUBE OIL BY SOLVENT EXTRACTION CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of US. Pat. application Ser. No. 875,502, filed Nov. 10, 1969 by Sheldon L. Thompson, which in turn is a continuationin-part of US. Pat. application Ser. No. 530,580, filed Feb. 28, 1966, by Sheldon L. Thompson, both now abandoned.

BACKGROUND OF THE INVENTION This invention broadly relates to the improvement in quality stability of lubricating oils. It is more particularly related to improving the stability of lubricating oils which have been hydrogenated under certain conditions, against degradation in color and sludge formation which results when such are exposed to actinic radiation and oxygen. Still more particularly, the invention relates to solvent extraction of hydrocracked lubricating oil stocks to substantially improve the color and sludge problems.

Various processes have been used from time to time for upgrading lubricating oil stocks. These have generally involved either solvent extraction or hydrogenation including hydrocracking treatment. In more recent times, there has been a demand for lubricating oils having an increased viscosity index. Recent developments in hydrocracking techniques in particular, or hydrotreating techniques, as some prefer to call it, has spawned and increased interest in commercial utilization of such hydrogenation processes as a lubricating oil stock upgrading method to obtain lubricating oils with an increased viscosity index. Generally the viscosity index of the full range lube fraction dewaxed to a F. pour point product lube oil will be 115 or higher. Briefly, this has involved catalytic hydrocracking of the lubricating oil stock at a temperature on the order of about 650 F. and above at high pressures. While such processes have greatly enhanced the viscosity index of the lubricating oil stocks so treated, they have simultaneously caused said stocks to exhibit a marked increase in color degradation on exposure to ultraviolet light and also to form greater amounts of sludge in the presence of oxygen during such exposure. It would be highly advantageous and, consequently, it is desirous to provide a method for alleviating these problems of quality stability.

It is, therefore, the main object of the present invention to substantially reduce the extent of color degradation in lubricating oil stocks which color problems occur upon exposure of a hydrotreated oil to actinic radiation, such as ultraviolet light and oxygen. It is another objectfto reduce the sludge-forming characteristics of a lube oil under such conditions. Other objects are to prepare lubricating oils in high yields, having a high viscosity index, and of improved stability. It is a still further object to accomplish each of the foregoing objects, in an economical fashion. It is yet another object to accomplish the foregoing objects by a simple and expedient process requiring simple, conventional and inexpensive equipment. Other objects will become apparent from the comments found herein.

SUMMARY OF THE INVENTION To the accomplishment of the foregoing and related vention in its broadest aspect, yet another broad aspect constitutes the preparation of lubricating oils having a high viscosity index and good qualitystability in regard to both color and sludge in the presence of ultraviolet radiation and oxygen, which comprises, in combination, hydrocracking or hydrotreating a lubricating oil stock followed by successive extractions of the sotrea'ted lube oil stock with a selective solvent having a preferential solubility for aromatics in not less than two extraction stages at a temperature below the miscibility temperature which is generally below about 300 F. and a temperature above that at which solids are formed.

It has been observed by many workers that lubricating oil stocks exhibit a degree of quality instability in the presence of actinic radiation, particularly ultraviolet light, and oxygen. Specifically, they tend to form sludge upon exposure to oxygen and actinic radiation. It has been noticed by many workers that lubricating oil stocks which have been hydrogenated'and especially where hydrocracked, are improved in properties in many respects but are also found to experience-significant difficulties of this nature. I have found that these problems are caused by some aromatic compounds of unknown specific structures. I have found that the troublesome configuration probably involves multiple rings. The surprising part of this is that hydrogenation processes, particularly the more recent ones, for example, as defined in US. Pat. Nos. 2,779,711; 2,917,448; 2,960,458; 3,046,218; 3,078,238 and 3,078,221, experience this problem despite the fact that certain color bodies are destroyed by suchhydrogenation processes and particularly the multiple-ringed aromatics. I have evidence to show that nothwithstanding the fact that certain troublesome multiple-ringed configurations are destroyed by hydrogenation processes and especially hydrocracking under the severe conditions employed in same; nevertheless, certain color body and sludge body precursors believed to be of multiple-ringed structure are present following the hydrogenation process when it is conducted at severe conditions including a temperature above about 650 F. These precursors are then able to form color bodies and sludge following the hydrogenation. The problem materials which are present whether they are formed by the hydrogen treatment as is believed to be the case or whether certain inhibitors present theretofore are destroyed by the hydrogenation whereby their inhibiting effect is lost, thereafter exhibit a decided instability in thepresence of actinic light and oxygen with the results that quality degradation in regard to both color and sludge occurs. In either case, the result is not achieved if the oil is first extracted and then hydrogenated and the process sequence in a combination hydrogenation and stabilizing selective extraction is accordingly seen to be extremely critical. It is an essential feature of this invention. Different known extractions commonly employed in refining on the other hand can be performed in their usual sequence including prior to hydrogenation where desired.

HYDROCRACKING The selective extraction of this invention may be advantageously used in combination with any hydrocracking process which employs temperatures above about 650 F. together with high pressures, those processes defined in US. Pat. Nos. 2,917,448; 2,960,458; 3,046,218; 3,078,221; 3,078,238 and 3,088,908 are preferably used, particularly for hydrocracking where such is desired. The teachings of those patents are hereby incorporated by reference.

The feed materials suitable for hydrogenation herein are any heavy petroleum fraction boiling in the lube oil range. In order that lube yields in this step be high the full boiling range hydrocracker charge on a dewaxed to a F. pour point basis generally should have a viscosity index of at least 60 and preferably at least about 75. Generally the full boiling range feed material on a dewaxed to a 0 F. pour point basis will not have a viscosity index of over 100, due to economic consideration. The source of the crude fraction is not critical although other properties are important to the attainment of high lube yields, long catalyst life, etc. Thus the lube source can be any which contains lubricating oil components such as crudes from Pennsylvania, Texas, California, Venezuela or Kuwait.

The hydrocracking process conditions disclosed in U.S. Pat. No. 2.960,458 are particularly preferred for use as the hydrocracking step in the present invention. In brief, this hydrocracking is accomplished by subjecting a deasphalted residuum having a viscosity index of between about 75 and 100 and a viscosity at 210 F. of between 90 and 200 SUS to hydrocracking at the temperature between about 735 and 825 F. and a pressure above about 2,500 p.s.i. and a space velocity of from 0.4 to 1.5. The hydrocracking is carried out in the presence of a catalyst having both aromatic saturation and ring scission activity, for example a nickel sulfide and tungsten sulfide in about a 1:1 to 4:1 ratio. The product from the hydrocracking is subjected to dewaxing (when necessary) and is then distilled to yield components which directly or when blended with each other meeth the SAE specification for a multigrade lubricating oil and have a V.I. of about 1 or above. The starting material is a residual petroleum fraction free of asphalt which has a V.I. of from 75 to 100.

SELECTIVE EXTRACTION It is, of course, known that there are selective solvents for aromatic compounds. It is also known that selective extraction at low temperatures causes the selective solvent to increase its selectivity for aromatics generally. It is, however, not known that such solvents employed at relatively low temperatures would be effective to greatly reduce the color and sludge problem present after the hydrogenation, and in fact would be highly selective for elimination of the color and sludge nroblems without a great loss in yield as a result of the extraction. It is believed this occurs by selective removal of the precursors.

It has been found that to accomplish the desired results of reduced quality degradation as to both sludge and color, not only is the temperature of the extraction important, but the number of stages is critical. The

4 x number of stages, however, is somewhat dependent on the amount of solvent. It should be kept in mind in any discussion of these two variables that they vary in inverse fashion with respect to each other. When one is increased, the other is to be decreased. It has been discovered that the sludge formation is substantially eliminated in some instances with only two stages but that the color instability is not reduced to the desirable level unless at least about five stages are employed or unless excessive quantities of solvent are employed. While more stages can be employed, it is not contemplated that more than seven stages will be employed primarily because the slight degree of improvement by these added stages does not justify the cost of conducting same and they reduce the yield. Generally from 3 to 7 stages will be found entirely suitable and preferred, and

from 5 to 7 stages are most preferred. When utilizing a continuous extraction technique such as a rotating disc contactor or a colurrm the number of stages is determined by emperically comparing the extraction ob.- tained with that obtained using separatory funnels according to the procedure described in the article Bench Scale Liquid Extraction Techniques by Edward G. Scheibel, INDUSTRIAL AND ENGINEER- ING CHEMISTRY, Vol. 49, No. 10, October, 1957, pp. 1679-1684.

The ratio of solvent to oil that can be employed in the extraction is not critical and ratios varying over a wide range can be employed; however, advantages are obtained in using certain ratios. Generally, a ratio in excess of 211 of a solvent to oil is not employed because such increases the economic cost of the process due to the large volume of the solvent to be handled and a reduction in the yield of lubricating oil product. On the other hand, ratios lower than about 0.25:1 require a compensating increase in the number of stages to achieve the desired effect. Ratios of solvent to oil on the order of from 0.75:1 to 05:1 are preferably employed.

The temperature, of course, will vary with the particular solvent in a given case. The minimum temperature is usually determined by the dewaxing temperature employed. The reason for this, of course, is that when a temperature below the dewaxing temperature is employed, solids are formed and this is not desired. The temperature is selected in every case to that the extraction stage is entirely in liquid phase. However, generally, a temperature in the range of above about 0 to 300 F. and more usually above about 0 to 250 F. is employed with any of those solvents taught herein. In the case of furfural, which is the most preferred solvent, a temperature in the range above about 0 F. to about I50 F. may be suitably employed; however, a temperature on the order of about to F. is preferred. The next preferred solvent is acetophenone and substantially the same temperature may be employed with it as the furfural, although the preferred temperature will vary on occasion.

Other examples of solvents that can be employed in this process are the following, either alone or in a mixture, with or without a selectivity improver:

acetophenone acetonitrile nitrobenzene aniline 2,2'-dichlorodiethyl ether dimethyl sulfoxide phenol The foregoing specifically named solvents are not exhaustive of such solvents since it-is contemplated and will be appreciated by those skilled in the art that any solvent having marked preferential solubility for aromatics can be employed in this invention though, of course, not with equal efficiency; and accordingly, all such solvents are not to be regarded as full equivalents.

The apparatus which can be employed to conduct the process is not special and any of the conventional solvent extraction equipment may be employed for same. Illustrative but non-limiting examples are rotating disc contactors, Podbielniak reactors, and countercurrent extraction columns and the like. Of the apparatus aforementioned, I prefer to employ rotary disc contactors or columns in carrying out the invention. It will be appreciated that the extraction can be carried out in either a batchwise operation as well as continuous, although the latter is more convenient and will be generally preferred. The equipment need not be adapted for special pressure conditions because atmospheric pressure is preferred, although atmospheric and superatmospheric pressures can be used.

Having now discussed the invention in broad and general terms and certain features with varying degrees of particularity, it is believed that any further discussion of the invention will be more beneficial in conjunction with detailed working examples. It is to be understood that the examples found hereinbelow are merely illustrative and are not limiting, the same being offered merely to facilitate the understanding of the present invention. It is to be further understood, of course, that the requisite variables are more or less interdependent and particularly the amount of solvent and the number of stages as has been pointed out herein. When one variable is arbitrarily fixed, the limits within which others may be varied are somewhat restricted. The more desirable ranges for ordinary application of my invention are indicated herein, and these can also be ascertained from the specific illustrative examples which include specific illustrative conditions presented herein. However, for any particular application of my invention, the most desirable conditions can be readily determined by routine trial by one skilled in the art, such a determination being facilitated by the discussion of trends of the variables presented herein and in the examples.

It is also to be understood that I am not bound by any theory-as to the mechanism of the presence or elimination of the color and sludge problem but only by the claimed process features which produce the effect of their presence or their absence and particularly the latter insofar as the elimination of quality degradation is desired where it occurs and my process discovery does eliminate that problem. The fact that yields of about 97 percent of stable lube oil as based on the unextracted hydrocracked oil can be obtained as illustrated in Example I, below is accounted for by this theory. Such yields are readily obtained by selecting solvent dosages and temperatures which are varied inversely to maintain this yield.

DESCRIPTION OF THE DRAWING The FIGURE is a diagrammatic flow scheme of a general and basic refinery scheme showing the relative order of the primary steps to be performed in the preparation of lubricating oils according to this invention.

The FIGURE is explained in more detail in conjunction with a working example in Example I.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE I HYDROCRACKING REFINING PROCEDURE Referring now to the FIGURE to facilitate the understanding of the invention and particularly the sequence relationship to the general or basic refining scheme a detailed example will be set forth.

A charge stock of Grade B solvent lube crude mix was charged to crude still 1 and fractionated into approximately percent and 30 percent of overhead and bottoms, respectively. The bottoms had an initial boiling point of 650 F. at atmospheric pressure. The bottoms were charged to a vacuum still 2 and fractionated to produce a gas oil, a distillate stock and a residual asphalt stock; the latter two had initial boiling points of about 695 F. and 750 F., respectively. The residual stock was deasphalted and extracted by the Duo-Sol process (i.e., which employs propane and a mixture of phenol-cresol as solvents) in deasphalter 3 at approximately 130 F. The raftinate from the deasphalter and the distillate stock from the vacuum still when combined had the following properties:

HYDROCRACKER CHARGE PROPERTIES Gravity, "API 305 Vacuum distillation range at 2 mm.

adjusted to 760 mm.

The foregoing mixture was charged to a hydrotreater 4 and said material was hydrocracked in the manner described in U.S. Pat. No. 2,960,458. A refinery hydrogen stream comprising gas and hydrogen, of which about percent was hydrogen, was used in the hydrocracking reaction.

The crude hydrocracked product was charged to a stripper or atmospheric still 5 and fractionated to produce gas, naphtha and fuel oil and a waxy lube of initial boiling point of approximately 700 F. which waxy lube was charged to a dewaxer 6 and dewaxed to a pour point of approximately 0 F. At this point, a product of about 116 viscosity index was obtained. The quality stability is reported below.

STABILIZING EXTRACTION PROCEDURE Pressed oil from the dewaxer above was then charged to a two-stage furfural rotating disc contactor 7 and was extracted at a temperature of approximately 120 F. using approximately volume percent of furfural to produce a raffinate comprising approximately 97 percent of the charge to the extractor. Although it is preferred that the extractor be located as here in position 7, it can be located in alternate positions shown by 9, 10 or 11 through 14 in the FIGURE. The raffmate then was distilled to produce three distillate fractions; 1, 2 and 3 and a bright-stock. The properties of these products are as follows;

Test Bright- Distillate method No 1 No. 2 No. 3 stock Viscosity, SUS/ 100 F. D2161 108 219 564 2262 Viscosity, SUS/210 F. D2161 40.3 48.8 69.8 156 Viscosity index D567 107 l 11 106 105 Flash point, "F. D92 400 455 535 600 Fire. "F. D92 7 4 4 9, 655

Pour point, F. LD9J .5. 25.. :5

Color D1500 0.25 0.75 1.25 3.0

Gravity, API D287 34.1 33.6 32.2 29.3

Aniline poigt. F. D611 222 241 Wt. percent aromatics J-7 6.6 4.9 6.3 7.3 Vacuum distillation range at 2 mm.

adjusted to 760 mm.:

IBP, F. 431 679 846 933 Recovery. percent STABILITY TEST PROCEDURE The distillate fractions then were tested for stability on exposure to ultraviolet light and oxygen. For comparison purposes, tests were made on typical commercial product produced by methods which do include hydrocracking as well as on material produced by the hydrocracking procedure above, but which was not extracted according to the present invention.

The stability test procedure employed was as follows: A 30 m1. sample of the material to be tested was placed in a 100 ml. beaker. Two 275 watt ultraviolet sunlamps were placed approximately 12 inches away from the surface of the sample. The sample was placed in an air ventilated oven on a rotating table and heated to F. The ultraviolet light was turned on when the sample was placed in the oven. After 45 hours, color of the test samples were determined using the ASTM D1500 test. The sludge formed was determined qualitatively by visual observation. The results of the color and sludge tests are reported in Table I as follows:

EXAMPLE III Pressed oil product from the Hydrocracking Refining Procedure of Example I was extracted with 50 percent by volume of furfural at approximately 80 F. in a num- A series of three two-stage furfural extraction runs were made at 120 F. on a pressed oil obtained from the procedure in Example I at varying solvent concentrations to determine the general effect of same. Using the test procedures of Example I, the following results were obtained:

50% 100% I50% Solvent Solvent Solvent Treatment Charge Dosage Dosage Dosage A B Initial Color, D1500 1.25 0.75 0.50 0.25 D1500 Color after the Stability Test 5.75 4.00 3.50 3.00 Sludge Medium Haze Haze Haze EXAMPLE V Other observations from the experimentation carried out are that a seven-stage extraction of Example I pressed oil at 80 F. employing percent by volume of furfural did not improve the initial color over a fivestage extraction (since it could not improve on a color of 0). However, the seven-stage extraction did effect an improvement in stability over the five-stage extraction. Therefore, initial cologis not alone a satgfagtpry test TABLE 1 Pressed oil product from the l-lydrocracking and Refining Procedure of Example I was extracted using the same general procedure as in Example I with acetophenone as the solvent. Five contacts at 100 volume percent dosage and -80 F. were used.

Using the Stability Test Procedures of Example I, it was found that the oil was decolorized from an initial D1500 color of 1.25 to 0.25 and after 45 hours exposure to UV. light the color only increased to a D1500 color of 0.5 while untreated charge increased to a color of 5.25.

Product obtained by hydrotreating Typical commercial product Unextracted Extracted Distillate fraction #1 #2 #3 #1 #2 #3 #1 #2 #3 D1500 Int. color 05 0.75 1.25 0.25 0.75 1.25 0.25 0.25 0.75

0.75 0.75 1.0 D1500 colorafterthe L, 2. 5 2 5 3 5 5 .5 4.5 4.5 3.0 3.0 3.25

m nes..-

Sludge Light Haze None Heavy Medium Haze Medium Light None EXAMPLE II of the advantages of the present invention. Data from which this conclusion is drawn is reported in the table below.

9 EXAMPLE v1 A furfural extraction carried out at about 170 F. according to the procedure of Example 1, and a solvent ratio to oil of 2:1 brought about some improvement in the stability, however, as those skilled in the art know, such conditions are generally not desired with furfural since they result in poorer yield of oil.

EXAMPLE VII Example VIl illustrates that lube oils which have been hydrocracked at above 650 F. suffer from color instability.

Two lube distillate fractions approximating conventional 100 and 500 neutral distillates in boiling range and viscosity were solvent refined at conventional commercial solvent refining conditions with selecto (i.e., a mixture of phenol and cresylic acid). The so-refined distillates were stable according to commercial standards and had the following typical properties:

EXAMPLE V111 A lube distillate approximating a 500 neutral fraction which had been hydrocracked according to the procedure described in US. Pat. No. 2,960,458 at about 735 F. and a L.H.S.V. of about l'was then solvent extracted in a 7-stage known simulated counter-current extraction procedure (i.e., using separatory funnels according to the procedure described in the article Bench Scale Liquid Extraction Techniques by Edward G. Scheibel, INDUSTRIAL AND ENGINEER- ING CHEMISTRY, Vol.49, No. 10, October 1957, pp. 1679-1684) using a furfural dosage of 200 percent and a temperature of about 80 F. A comparison of the spectral curves of the extracted and unextracted oils from solutions thereof in isooctane shows that the furfural extraction has reduced the amount of condensed ring polynuclear aromatic compounds containing three or more rings.

EXAMPLE 1X A series of runs were carried out as follows:

The foregoing charge was vacuum distilled and the heaviest fraction (comprising about 23 percent of the crude) was propane deasphalted (yield of oil about 50 percent) to produce fractions boiling in the ranges below:

Boiling Range about 775 to 855F. about 855 to 955F.

about 955F. and above Light Vacuum Distillate Heavy Vacuum Distillate Deasphalted Oil A portion of heavy vacuum distillate and deasphalted oil were extracted with furfural at conditions approximating the following:

' Solvent Temper- Raffinate viscosity 500 Neutral 100 Neutral Dosage ature Yield a Heavy Vacuum Distillate 150% 220F. about 69% Viscosity Index 99 100 Deasphalted Oil 300% 220 F. about 80% Gravity, AP! 30.1 33.8 5 I Boiling Range, F., These fractions had the following approximate prop- 5-95% PT. 777-1012 684-787 erties. Color, ASTM D1500 Initial 1.25 0.75 Final (after 45 hrs.) 3.25 2.50 unextracted Extracted S lyg ge N 0W4 M 11 5 9 Wt. A P| Con- Wt. AP1 Aromatics Grav ty radson Aromatics Gravity The foregoing oil fractions were treatedwith hydro- Heavy 60 gen under pressure over a sulfided cobalt-molybdenum Vacuum oxide on alumina catalyst in a series of runs wherein the gg fi d 22 37 29 6 conditions and resulting stability were as follows: 95L p 52 22 L9 26 TAELE 111 Run No.

1 2 3 4 5 6 7 8 9 i0 11 12 13 14 15 Charge stock 500 Same Same Same Same Same Same Same Same Same Same 100 Same Same Same Neutral Neutral Press" p.s.i.g. 500 500 500 500 500 500 1000 1000 500 500 500 500 500 500 500 Temp.,F. 600 650 700 750 650 750 650 750 650 700 750 450 550 650 750 LESNAWLL l 1 1 2 2 1 1 1 1 1 2 z 1 1 Color, ASTM D1500:

Initial 0.25 0.50 1.25 2.25 0.75 2.00 0.25 1.25 0.75 1.00 1.25 0.25 0.25 0.75 1.75 Firtiglisafter 1.0 1.75 3.5 5.0 2.5 4.5 2.25 3.5 2.5 2.75 4.5 1.25 1.25 1.5 3.0

rs.) SliTdge None Haze Very Very Haze None None None None None Light Light Light Light Light Light The materials of the foregoing character were blended to prepare comparative feeds for hydrocracking as follows:

Feed Type Feed Type No. 1 No. 2 (i.e., Un- (i.e., 3 extracted) Extracted) Light Vacuum Distillate, 24 29 Heavy Vacuum Distillate, 29 Deasphaltcd Oil, 47 Extracted Heavy Vacuum Distillate, 24 Extracted Deasphalted Oil, 47 Aromatic Content, 50 37 API Gravity, F. 24 28 181 694 706 5% 755 762 10% 784 791 50% 917 940 E.P. 1030 1030 Receiver, 67 Conradson Carbon, wt. 1.0 Viscosity at F. 217 Viscosity at F. 41 35 Viscosity at 210F. 16 15 Waxy V.l. 79-80 112-113 V.l. dewaxed to 0F. g pour point 59 about 116 The blended charges of the foregoing character were hydrocracked at conditions approximately as follows:

Typical results on a dewaxed basis were as follows:

Yield, based on Vol. 39.4 45.7 charge to hydrocracker Yield, based on Vol. 9.6 9.1

of crude V.I. Range 105-115 102-110 That the hydrocracked and dewaxed product was mm o vsnteat i t uh m1 .!s1 7-stage procedure described in Example VIII with furfural at about 120 F. using a solvent dosage of about 100 percent. Ihg stz bilized Feed type No. 1 Feed type No. 2

Color Color Product fraction Initial Final Sludge Initial Final Sludge 100 N 0.75 2.00 Lt. med. 0.25 2.0 V. It. 200 N 0.75 1.75 V. lt. 0.50 2.0 None 500 N 1.5 2.25 I-Iaze 1.25 3.25 None Brightstock 7.0

7.50 None For further comparison purposes the typical stability characteristics of unstabilized hydrocracked product of Feed Type No. 2 were as follows:

' Color Initial Final Sludge 100 N 0.75 7.00 Lt. Med. 200 N 1.25 7.00 Lt. Med. 500 N 2.25 6.00 Light Brightstock (Too dark) (Too dark) Light An analysis was made for the typical aromatic content of the charge to the stabilizing extraction and of the stabilized lube product (i.e., the raffinate) and in one case of the extract, the results were as follows:

Feed Type Feed Type No. 2 No. l Aromatic, (approx.) Charge 15.7 10.8 Raffinate 14.4 10.5 Extract 51 Total Raffinate Yield, (approx.) 97 97 EXAMPLE X A blend of light vacuum distillate and partially furfural extracted heavy vacuum distillate (i.e., similar to that defined in Example IX from a Lagomedio crude were hydrocracked according to the procedure in US. Pat. No. 2,960,458 at about 750 F. and a I...I-I.S.V. of about 1. The hydrocracked product was then solvent extracted with phenol in a 3-stage simulated countercurrent extraction in which .the temperature was maintained in the range of about 120-130 F. and a solvent dosage of about 75 percent was employed.

The raffinate was then tested for stability in the ASTM D1500 test along with a standard and the results were as follows:

Initial Final Sample Color Color Haze Sludge Hydrocrucked ()il N 0.25 4.25 hvy.med. hvy. N 0.50 4.25 hvy. medium 200 N 1.25 4.50 hvy. medium Extrncted (or stubilizcd) Oil 70 N 0.25 2.50 med. light 100 N 0.25 2.00 med. light 200 N 0.25 1.25 med. v. 11. 360 N 3.00' 3.50 med. light Yicld (total rutfiniatc. approx.) 97% In the foregoing examples the final solvent extraction to achieve stability of the hydrocracked lube does not significantly alter the V1 of the hydrocracked lube.

The invention claimed is:

1. A process of preparing lube oils with a viscosity index of at least 1 15 on a dewaxed to 0 F. pour point basis and having high quality and sludge-forming properties which comprises in combination in the following sequence, hydrocracking a suitable lube oil fraction having a viscosity index of from about 60 to 100 on a dewaxed to 0 F. pour point basis with hydrogen at pressures above about 1,500 p.s.i. and temperatures above about 650 F. in the presence of a lube oil hydrocracking catalyst, and subsequently selectively extracting said hydrocracked lube oil fraction by serially extracting same in at least two stages with a solvent selected from the class consisting of furfural, acetophenone, acetonitrile, nitrobenzene, aniline, 2,2- dichlorodiethyl ether, dimethylsulfoxide and phenol, at a solvent to oil ratio not in excess of about 2:1 at a temperature in the range of about 0 to 300 F., and controlling the extraction temperature and solvent dosages within said ranges to provide for a raffimate yield of approximately 97 percent with the particular solvent employed.

2. The process of claim 1 wherein the solvent is furfural.

3. The process of claim 2 wherein the hydrocracking is carried out at a temperature of from about 735 F. to about 825 F. and a pressure of at least about 2,500 p.s.i.

4. The process of claim 3 wherein the number of said extraction stages is not less than three and the extraction temperature is in the range of 0 F. to about 250 5. The process of claim 4 wherein the lubricating oil stock is dewaxed after the hydrocracking step and before the solvent extraction step.

,6. The process of claim 5 wherein the ratio of furfural to lubricating oil in the solvent extraction step is in the range of about 0.25:1 to 2.021.

7. The process of claim 6 wherein the extraction temperature is from 0 to F.

8. The process of claim 7 wherein the hydrocracking is carried out at a temperature of from about 735 F. to about 825 F. and a pressure of at least about 2,500

p.s.i.

9. The process of claim 8 wherein the number of ex- 13. The process of claim l l wherein tli e solvent is acctophenone.

14. A process of preparing lube oils with a viscosity index of at least about 100 on a dewaxed to F. pour point basis and having high quality and sludge-forming properties which comprises in combination in the following sequence, hydrocracking a suitable lube oil fraction having a viscosity index of below about 100 on a dewaxed to 0 F. pour point basis, with hydrogen at pressures above about 1,500 p.s.i. and temperatures above about 650 F. in the presence of a lube oil hydrocracking catalyst, the severity of said hydrocracking being sufficient to increase the viscosity index of said suitable lube oil fraction at least about 24 viscosity index units, and subsequently selectively extracting said hydrocracked lube oil fraction by serially extracting same in at least two stages with a solvent selected from the class consisting of furfural, acetophenone, acetonitrile, nitrobenzene, aniline, 2,2'- dichlorodiethyl ether, dimethylsulfoxide and phenol, at a solvent to oil ratio not in excess of about 2:1 at a temperature in the range of about 0 to 300 F., and controlling the extraction temperature and solvent dosages within said ranges to provide for a raffinate yield of approximately 97 percent with the particular solvent used.

15. The process of claim 14 wherein the lube oil fraction being fedto the hydrocracker has a viscosity index of from about 60 to 100 on a dewaxed to 0 F. pour point basis,

16. The process of claim 15 wherein the solvent is furfural.

17. The process of claim 16 wherein the number of extraction stages is not less than three.

18. The process of claim 17 wherein the ratio of furfural to lubricating oil in the solvent extraction step is in the range of 0.25:1 to 2.021.

19. The process of claim 19 wherein the hydrocracked lube product has a viscosity index of at leastv UNE'TEB STATES PATENT OFFICE Patent No- ;3,781 ,196 Dated December 25, 1973 Sheldon L. Thompson Inventor(s) It is certified that error appears in the above-identified patent and that said" Letters Patent are hereby corrected as shown below:

- Insert the attached sheet as part of Letters Patent Signed and sealed this let day of October 1974.

(SEAL) A'ttest:

' McCOY M. GIBSON JR. C. MARSHALL DAN-N Attesting Officer Commissioner of Patents FORM P0405) (10-6 USCOMM-DC 60376-P69 U.S. GOVERNMENT PRINTING OFFICE: 8 9 Q3 0 

2. The process of claim 1 wherein the solvent is furfural.
 3. The process of claim 2 wherein the hydrocracking is carried out at a temperature of from about 735* F. to about 825* F. and a pressure of at least about 2,500 p.s.i.
 4. The process of claim 3 wherein the number of said extraction stages is not less than three and the extraction temperature is in the range of 0* F. to about 250* F.
 5. The process of claim 4 wherein the lubricating oil stock is dewaxed after the hydrocracking step and before the solvent extraction step.
 6. The process of claim 5 wherein the ratio of furfural to lubricating oil in the solvent extraction step is in the range of about 0.25:1 to 2.0:1.
 7. The process of claim 6 wherein the extraction temperature is from 0* to 150* F.
 8. The process of claim 7 wherein the hydrocracking is carried out at a temperature of from about 735* F. to about 825* F. and a pressure of at least about 2,500 p.s.i.
 9. The process of claim 8 wherein the number of extraction stages is not less than three and the extraction temperature is in the range of 0* F. to about 250* F.
 10. The process of claim 9 wherein the lubricating oil stock is dewaxed after the hydrocracking step and before the solvent extraction step.
 11. The process of claim 10 wherein the ratio of solvent to lubricating oil is in the range of about 0.25:1 to 2.0:1.
 12. The process of claim 11 wherein the solvent is phenol.
 13. The process of claim 11 wherein the solvent is acetophenone.
 14. A process of preparing lube oils with a viscosity index of at least about 100 on a dewaxed to 0* F. pour point basis and having high quality and sludge-forming properties which comprises in combination in the following sequence, hydrocracking a suitable lube oil fraction having a viscosity index of below about 100 on a dewaxed to 0* F. pour point basis, with hydrogen at pressures above about 1,500 p.s.i. and temperatures above about 650* F. in the presence of a lube oil hydrocracking catalyst, the severity of said hydrocracking being sufficient to increase the viscosity index of said suitable lube oil fraction at least about 24 viscosity index units, and subsequently selectively extracting said hydrocracked lube oil fraction by serially extracting same in at least two stages with a solvent selected from the class consisting of furfural, acetophenone, acetonitrile, nitrobenzene, aniline, 2,2''-dichlorodiethyl ether, dimethylsulfoxide and phenol, at a solvent to oil ratio not in excess of about 2:1 at a temperature in the range of about 0* to 300* F., and controlling the extraction temperature and solvent dosages within said ranges to provide for a raffinate yield of approximately 97 percent with the particular solvent used.
 15. The process of claim 14 wherein the lube oil fraction being fed to the hydrocracker has a viscosity index of from about 60 to 100 on a dewaxed to 0* F. pour point basis.
 16. The process of claim 15 wherein the solvent is furfural.
 17. The process of claim 16 wherein the number of extraction stages is not less than three.
 18. The process of claim 17 wherein the ratio of furfural to lubricating oil in the solvent extraction step is in the range of 0.25:1 to 2.0:1.
 19. The process of claim 19 wherein the hydrocracked lube product has a viscosity index of at least
 115. 